to demolish containing walls or to propel a movable object. Explosives of many kinds have been developed and are still being developed for both uses; the two types cannot be interchanged.
History . Greek fire , a prototype of gunpowder, was fist used as a liquid flame in a 7th - century naval battle. Black powder , consiting of sulfur , saltpeter , and carbon, was supposedly used by the Chinese in fireworks many centuries before it was introduced in Europe, in the 14th century , as a propellant for guns and for demolition work in mines. In 1845 the first high explosive , solid nitrocellulose or guncutton , was inveted , and the following year liquid nitroglycerin was discovered. They are difficult to handle , and in 1863 Alfred Nobel produced solid dynamite using nitroglycerin . Research since then has developed hundreds of specialized explosives that include picric acid , ethly nitrate , mercury fulmianate and TNT. Most explosive are mixtures of ingredients such as synthenic nitrogen compounds, mineral nitrates , combustibles , and chemicals that prevent freezing and provide protection againts slow decomposition, all in proportions determined by actual experimentation.
Method of Use. The mechanism for exploding explosive is the same whatever the composition, and the force of the explosion depends on the speed with which the reaction proceeds and the amount of gas and heat liberated. The speed varies from 1 mi. to over 3 mi. per second. Small amounts of most explosives when ignited in the open air will burn and dissipate their heat and gases harmlessly.Different explosives are packaged differently to obtain maximum effect. For demolition work the charge is calculated by the operator and placed in various ways. Often the atmosphere itself is used as a containing wall, whose very porosity resists the sudden expansion and forces it downward into the solid ground instead. In all modern firearms and for all military guns, the charge is determined by the manufacture of the ammunition.
The charge is set off by a detonator , an explosive that produces a shock wave hard enough to compress or jar the ingredients of the charge into reacting. The detonator , or the blasting cap , of which there are many kinds, itself fired by a burning fuse, an electric spark, or a firing pin.
Commercial explosives are used in coal and metal mines to blast the solid ore into pieces that can be handled ; they are used to drill holes or drive tunnels and for earth-mov-ing work in the construction of canals, dams, railroads, highways, and harbor facilities. Commercial explosive are too powerful for gunsm while powders for military and sporting weapons are too weak for blasting and they also produce noxious fumes. Explosive for many kind of propellant must be made to exacting standards which will guarantee a certain effect per unit weight.
E. I. Du Pont De Nemours & Co.